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4 5<book id="Z85230Guide">
6 <bookinfo>
7 <title>Z8530 Programming Guide</title>
8 9 <authorgroup>
10 <author>
11 <firstname>Alan</firstname>
12 <surname>Cox</surname>
13 <affiliation>
14 <address>
15 <email>alan@lxorguk.ukuu.org.uk</email>
16 </address>
17 </affiliation>
18 </author>
19 </authorgroup>
20 21 <copyright>
22 <year>2000</year>
23 <holder>Alan Cox</holder>
24 </copyright>
25 26 <legalnotice>
27 <para>
28 This documentation is free software; you can redistribute
29 it and/or modify it under the terms of the GNU General Public
30 License as published by the Free Software Foundation; either
31 version 2 of the License, or (at your option) any later
32 version.
33 </para>
34 35 <para>
36 This program is distributed in the hope that it will be
37 useful, but WITHOUT ANY WARRANTY; without even the implied
38 warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
39 See the GNU General Public License for more details.
40 </para>
41 42 <para>
43 You should have received a copy of the GNU General Public
44 License along with this program; if not, write to the Free
45 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
46 MA 02111-1307 USA
47 </para>
48 49 <para>
50 For more details see the file COPYING in the source
51 distribution of Linux.
52 </para>
53 </legalnotice>
54 </bookinfo>
55 56<toc></toc>
57 58 <chapter id="intro">
59 <title>Introduction</title>
60 <para>
61 The Z85x30 family synchronous/asynchronous controller chips are
62 used on a large number of cheap network interface cards. The
63 kernel provides a core interface layer that is designed to make
64 it easy to provide WAN services using this chip.
65 </para>
66 <para>
67 The current driver only support synchronous operation. Merging the
68 asynchronous driver support into this code to allow any Z85x30
69 device to be used as both a tty interface and as a synchronous
70 controller is a project for Linux post the 2.4 release
71 </para>
72 </chapter>
73 74 <chapter id="Driver_Modes">
75 <title>Driver Modes</title>
76 <para>
77 The Z85230 driver layer can drive Z8530, Z85C30 and Z85230 devices
78 in three different modes. Each mode can be applied to an individual
79 channel on the chip (each chip has two channels).
80 </para>
81 <para>
82 The PIO synchronous mode supports the most common Z8530 wiring. Here
83 the chip is interface to the I/O and interrupt facilities of the
84 host machine but not to the DMA subsystem. When running PIO the
85 Z8530 has extremely tight timing requirements. Doing high speeds,
86 even with a Z85230 will be tricky. Typically you should expect to
87 achieve at best 9600 baud with a Z8C530 and 64Kbits with a Z85230.
88 </para>
89 <para>
90 The DMA mode supports the chip when it is configured to use dual DMA
91 channels on an ISA bus. The better cards tend to support this mode
92 of operation for a single channel. With DMA running the Z85230 tops
93 out when it starts to hit ISA DMA constraints at about 512Kbits. It
94 is worth noting here that many PC machines hang or crash when the
95 chip is driven fast enough to hold the ISA bus solid.
96 </para>
97 <para>
98 Transmit DMA mode uses a single DMA channel. The DMA channel is used
99 for transmission as the transmit FIFO is smaller than the receive
100 FIFO. it gives better performance than pure PIO mode but is nowhere
101 near as ideal as pure DMA mode.
102 </para>
103 </chapter>
104 105 <chapter id="Using_the_Z85230_driver">
106 <title>Using the Z85230 driver</title>
107 <para>
108 The Z85230 driver provides the back end interface to your board. To
109 configure a Z8530 interface you need to detect the board and to
110 identify its ports and interrupt resources. It is also your problem
111 to verify the resources are available.
112 </para>
113 <para>
114 Having identified the chip you need to fill in a struct z8530_dev,
115 which describes each chip. This object must exist until you finally
116 shutdown the board. Firstly zero the active field. This ensures
117 nothing goes off without you intending it. The irq field should
118 be set to the interrupt number of the chip. (Each chip has a single
119 interrupt source rather than each channel). You are responsible
120 for allocating the interrupt line. The interrupt handler should be
121 set to <function>z8530_interrupt</function>. The device id should
122 be set to the z8530_dev structure pointer. Whether the interrupt can
123 be shared or not is board dependent, and up to you to initialise.
124 </para>
125 <para>
126 The structure holds two channel structures.
127 Initialise chanA.ctrlio and chanA.dataio with the address of the
128 control and data ports. You can or this with Z8530_PORT_SLEEP to
129 indicate your interface needs the 5uS delay for chip settling done
130 in software. The PORT_SLEEP option is architecture specific. Other
131 flags may become available on future platforms, eg for MMIO.
132 Initialise the chanA.irqs to &amp;z8530_nop to start the chip up
133 as disabled and discarding interrupt events. This ensures that
134 stray interrupts will be mopped up and not hang the bus. Set
135 chanA.dev to point to the device structure itself. The
136 private and name field you may use as you wish. The private field
137 is unused by the Z85230 layer. The name is used for error reporting
138 and it may thus make sense to make it match the network name.
139 </para>
140 <para>
141 Repeat the same operation with the B channel if your chip has
142 both channels wired to something useful. This isn't always the
143 case. If it is not wired then the I/O values do not matter, but
144 you must initialise chanB.dev.
145 </para>
146 <para>
147 If your board has DMA facilities then initialise the txdma and
148 rxdma fields for the relevant channels. You must also allocate the
149 ISA DMA channels and do any necessary board level initialisation
150 to configure them. The low level driver will do the Z8530 and
151 DMA controller programming but not board specific magic.
152 </para>
153 <para>
154 Having initialised the device you can then call
155 <function>z8530_init</function>. This will probe the chip and
156 reset it into a known state. An identification sequence is then
157 run to identify the chip type. If the checks fail to pass the
158 function returns a non zero error code. Typically this indicates
159 that the port given is not valid. After this call the
160 type field of the z8530_dev structure is initialised to either
161 Z8530, Z85C30 or Z85230 according to the chip found.
162 </para>
163 <para>
164 Once you have called z8530_init you can also make use of the utility
165 function <function>z8530_describe</function>. This provides a
166 consistent reporting format for the Z8530 devices, and allows all
167 the drivers to provide consistent reporting.
168 </para>
169 </chapter>
170 171 <chapter id="Attaching_Network_Interfaces">
172 <title>Attaching Network Interfaces</title>
173 <para>
174 If you wish to use the network interface facilities of the driver,
175 then you need to attach a network device to each channel that is
176 present and in use. In addition to use the generic HDLC
177 you need to follow some additional plumbing rules. They may seem
178 complex but a look at the example hostess_sv11 driver should
179 reassure you.
180 </para>
181 <para>
182 The network device used for each channel should be pointed to by
183 the netdevice field of each channel. The hdlc-&gt; priv field of the
184 network device points to your private data - you will need to be
185 able to find your private data from this.
186 </para>
187 <para>
188 The way most drivers approach this particular problem is to
189 create a structure holding the Z8530 device definition and
190 put that into the private field of the network device. The
191 network device fields of the channels then point back to the
192 network devices.
193 </para>
194 <para>
195 If you wish to use the generic HDLC then you need to register
196 the HDLC device.
197 </para>
198 <para>
199 Before you register your network device you will also need to
200 provide suitable handlers for most of the network device callbacks.
201 See the network device documentation for more details on this.
202 </para>
203 </chapter>
204 205 <chapter id="Configuring_And_Activating_The_Port">
206 <title>Configuring And Activating The Port</title>
207 <para>
208 The Z85230 driver provides helper functions and tables to load the
209 port registers on the Z8530 chips. When programming the register
210 settings for a channel be aware that the documentation recommends
211 initialisation orders. Strange things happen when these are not
212 followed.
213 </para>
214 <para>
215 <function>z8530_channel_load</function> takes an array of
216 pairs of initialisation values in an array of u8 type. The first
217 value is the Z8530 register number. Add 16 to indicate the alternate
218 register bank on the later chips. The array is terminated by a 255.
219 </para>
220 <para>
221 The driver provides a pair of public tables. The
222 z8530_hdlc_kilostream table is for the UK 'Kilostream' service and
223 also happens to cover most other end host configurations. The
224 z8530_hdlc_kilostream_85230 table is the same configuration using
225 the enhancements of the 85230 chip. The configuration loaded is
226 standard NRZ encoded synchronous data with HDLC bitstuffing. All
227 of the timing is taken from the other end of the link.
228 </para>
229 <para>
230 When writing your own tables be aware that the driver internally
231 tracks register values. It may need to reload values. You should
232 therefore be sure to set registers 1-7, 9-11, 14 and 15 in all
233 configurations. Where the register settings depend on DMA selection
234 the driver will update the bits itself when you open or close.
235 Loading a new table with the interface open is not recommended.
236 </para>
237 <para>
238 There are three standard configurations supported by the core
239 code. In PIO mode the interface is programmed up to use
240 interrupt driven PIO. This places high demands on the host processor
241 to avoid latency. The driver is written to take account of latency
242 issues but it cannot avoid latencies caused by other drivers,
243 notably IDE in PIO mode. Because the drivers allocate buffers you
244 must also prevent MTU changes while the port is open.
245 </para>
246 <para>
247 Once the port is open it will call the rx_function of each channel
248 whenever a completed packet arrived. This is invoked from
249 interrupt context and passes you the channel and a network
250 buffer (struct sk_buff) holding the data. The data includes
251 the CRC bytes so most users will want to trim the last two
252 bytes before processing the data. This function is very timing
253 critical. When you wish to simply discard data the support
254 code provides the function <function>z8530_null_rx</function>
255 to discard the data.
256 </para>
257 <para>
258 To active PIO mode sending and receiving the <function>
259 z8530_sync_open</function> is called. This expects to be passed
260 the network device and the channel. Typically this is called from
261 your network device open callback. On a failure a non zero error
262 status is returned. The <function>z8530_sync_close</function>
263 function shuts down a PIO channel. This must be done before the
264 channel is opened again and before the driver shuts down
265 and unloads.
266 </para>
267 <para>
268 The ideal mode of operation is dual channel DMA mode. Here the
269 kernel driver will configure the board for DMA in both directions.
270 The driver also handles ISA DMA issues such as controller
271 programming and the memory range limit for you. This mode is
272 activated by calling the <function>z8530_sync_dma_open</function>
273 function. On failure a non zero error value is returned.
274 Once this mode is activated it can be shut down by calling the
275 <function>z8530_sync_dma_close</function>. You must call the close
276 function matching the open mode you used.
277 </para>
278 <para>
279 The final supported mode uses a single DMA channel to drive the
280 transmit side. As the Z85C30 has a larger FIFO on the receive
281 channel this tends to increase the maximum speed a little.
282 This is activated by calling the <function>z8530_sync_txdma_open
283 </function>. This returns a non zero error code on failure. The
284 <function>z8530_sync_txdma_close</function> function closes down
285 the Z8530 interface from this mode.
286 </para>
287 </chapter>
288 289 <chapter id="Network_Layer_Functions">
290 <title>Network Layer Functions</title>
291 <para>
292 The Z8530 layer provides functions to queue packets for
293 transmission. The driver internally buffers the frame currently
294 being transmitted and one further frame (in order to keep back
295 to back transmission running). Any further buffering is up to
296 the caller.
297 </para>
298 <para>
299 The function <function>z8530_queue_xmit</function> takes a network
300 buffer in sk_buff format and queues it for transmission. The
301 caller must provide the entire packet with the exception of the
302 bitstuffing and CRC. This is normally done by the caller via
303 the generic HDLC interface layer. It returns 0 if the buffer has been
304 queued and non zero values for queue full. If the function accepts
305 the buffer it becomes property of the Z8530 layer and the caller
306 should not free it.
307 </para>
308 <para>
309 The function <function>z8530_get_stats</function> returns a pointer
310 to an internally maintained per interface statistics block. This
311 provides most of the interface code needed to implement the network
312 layer get_stats callback.
313 </para>
314 </chapter>
315 316 <chapter id="Porting_The_Z8530_Driver">
317 <title>Porting The Z8530 Driver</title>
318 <para>
319 The Z8530 driver is written to be portable. In DMA mode it makes
320 assumptions about the use of ISA DMA. These are probably warranted
321 in most cases as the Z85230 in particular was designed to glue to PC
322 type machines. The PIO mode makes no real assumptions.
323 </para>
324 <para>
325 Should you need to retarget the Z8530 driver to another architecture
326 the only code that should need changing are the port I/O functions.
327 At the moment these assume PC I/O port accesses. This may not be
328 appropriate for all platforms. Replacing
329 <function>z8530_read_port</function> and <function>z8530_write_port
330 </function> is intended to be all that is required to port this
331 driver layer.
332 </para>
333 </chapter>
334 335 <chapter id="bugs">
336 <title>Known Bugs And Assumptions</title>
337 <para>
338 <variablelist>
339 <varlistentry><term>Interrupt Locking</term>
340 <listitem>
341 <para>
342 The locking in the driver is done via the global cli/sti lock. This
343 makes for relatively poor SMP performance. Switching this to use a
344 per device spin lock would probably materially improve performance.
345 </para>
346 </listitem></varlistentry>
347 348 <varlistentry><term>Occasional Failures</term>
349 <listitem>
350 <para>
351 We have reports of occasional failures when run for very long
352 periods of time and the driver starts to receive junk frames. At
353 the moment the cause of this is not clear.
354 </para>
355 </listitem></varlistentry>
356 </variablelist>
357 358 </para>
359 </chapter>
360 361 <chapter id="pubfunctions">
362 <title>Public Functions Provided</title>
363!Edrivers/net/wan/z85230.c
364 </chapter>
365 366 <chapter id="intfunctions">
367 <title>Internal Functions</title>
368!Idrivers/net/wan/z85230.c
369 </chapter>
370 371</book>
372